Denial of service attack via incorrect parameters to federation APIs
Published Dec 9, 2020
7.1
HIGHCVSS 4.0
EPSS 2.39%
Description
Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference "homeserver" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).
Affected products
-
- Version < 1.23.1StatusaffectedConstraints-
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Matrix-Org | Synapse | n/a |
|
Configuration 2
- 32
- 33
No data.
No Red Hat product state for this CVE.
No package ranges for this CVE.
Remediation
No remediation recorded yet.
Metrics
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
No CVSS v3.0 score for this CVE.
AV:N/AC:L/Au:S/C:N/I:N/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
- EPSS v4
Percentile over time
- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
- EPSS v4
Table of values (12 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 2.39% (0.02392) | 83.36th | v5 (v2026.06.15) |
| Jun 15, 2026 | 2.36% (0.02363) | 81.52th | v5 (v2026.06.15) |
| Mar 17, 2025 | 0.45% (0.00453) | 61.69th | v4 (v2025.03.14) |
| Dec 12, 2024 | 0.15% (0.00153) | 52.97th | v3 (v2023.03.01) |
| Nov 8, 2023 | 0.16% (0.00160) | 52.48th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.18% (0.00182) | 53.71th | v3 (v2023.03.01) |
| Mar 6, 2023 | 1.03% (0.01034) | 41.69th | v2 (v2022.01.01) |
| Apr 1, 2022 | 1.03% (0.01034) | 37.91th | v2 (v2022.01.01) |
| Mar 31, 2022 | 8.38% (0.08384) | 83.08th | v2 (v2022.01.01) |
| Jan 6, 2022 | 7.62% (0.07623) | 83.88th | v1 |
| Jan 5, 2022 | 1.81% (0.01806) | 75.23th | v5 (v2026.06.15) |
| Apr 14, 2021 | 1.81% (0.01806) | 0.00th | v1 |
References (11)
- https://github.com/advisories/GHSA-hxmp-pqch-c8mm Advisory
- https://github.com/matrix-org/synapse/blob/develop/CHANGES.md#synapse-1231-2020-12-09 x_refsource_MISCRelease NotesThird Party Advisory
- https://github.com/matrix-org/synapse/commit/3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b x_refsource_MISCPatchThird Party Advisory
- https://github.com/matrix-org/synapse/pull/8776 x_refsource_MISCPatchThird Party Advisory
- https://github.com/matrix-org/synapse/security/advisories/GHSA-hxmp-pqch-c8mm x_refsource_CONFIRMThird Party Advisory
- https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2020-236.yaml
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC/ vendor-advisoryx_refsource_FEDORA
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7/ vendor-advisoryx_refsource_FEDORA
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7
- https://nvd.nist.gov/vuln/detail/CVE-2020-26257
Change history (0)
No recorded changes yet.